import java.util.Objects;

interface A
{
    public String getInfo();
}

class B implements A
{
    public String getInfo()
    {
        return "Hello world";
    }
}

public class ZhaiZhiJie02
{
    public static void main(String[] args) {
        A a = new B();
        Object obj = a;
        A x = (A)obj;
        System.out.println(x.getInfo());
    }
}
